Microfluidic pumping devices are used in numerous applications, such as administration of medicine and biological and pharmaceutical research. Such pumping devices include mechanical pumps, such as syringe-type pumps and micromechanical pumps, and non-mechanical pumps, such as electrohydrodynamic pumps, electro-osmotic flow pumps, electrowetting pumps, and thermocapillary pumps.
There are drawbacks to different pumping devices. For example, a steady flow rate is difficult to achieve. Moreover, many mechanical pumps require an electrical power source, as do pumps that operate based on electrical properties. Many of these pumps are costly and often have slow response times.
Conventional syringe pumps are typically employed with either a syringe or a vial and plunger system for administering a liquid to a patient. In such conventional systems, a syringe or vial of the liquid is oriented vertically in a fixed position on the syringe pump. The bottom of the syringe or vial defines a discharge port connected to a flexible, hollow tubing which extends to the patient. The plunger or piston of the apparatus is engaged with the moving pusher plate or drive member of the syringe pump and is driven downwardly into the syringe body or vial to force the liquid agent from the syringe body or vial through the tubing and into the patient.
An example of such a syringe pump is described in a system of PCT published patent application WO03008102. The system employs a microchannel and a gravity driven pump comprising horizontally oriented fluid supply reservoirs. The pump supplies fluid to the microchannel at a substantially constant rate. The device may be used, among other things, for motile sperm sorting.